Structured surfaces have been used in various applications for optical benefits, surface energy modification, adhesive tack control, and drag reduction. For example, prismatic structures on the surface of photovoltaic panels reduce reflection and direct more light towards the silicon cells, thus increasing power output. Similar prismatic structures promote fluid flow over a surface resulting in reduced drag when applied to an automobile, boat, or the like, or to wind or water turbine blades. Structured surfaces can also be used to make hydrophilic surfaces hydrophobic.
Silicone elastomers are known for their stability under long-term ultra-violet light exposure, and they can be optically clear and tough, which makes them well suited for outdoor use. Replicated structured surfaces are commonly made out of silicones, especially using a platinum catalyzed addition cure silicone. This results in very well replicated surfaces but requires a catalyst, heating cycle and more expensive vinyl and hydride functional silicone fluids. Condensation cure silicones can be used but also require a catalyst and moisture for the reaction. The moisture is usually taken from the ambient air but during a microreplication process there is the problem of moisture diffusion since often the silicone is partially or fully covered by a tool or substrate. Therefore it can take a long time to cure. In addition, metal catalysts are expensive, are easily inactivated by contaminants, and residual catalyst in silicones can be undesirable. Peroxide cured silicones also require thermal cycles to initiate cross-linking and have the issue of peroxide byproducts, such as organic acids or alcohols, which need to be removed with additional heating. There is also usually some discoloration associated with peroxide cured silicones.
In general, the currently available cross-linkable silicones, utilizing platinum catalyzed addition cure systems, tin catalyzed moisture/condensation cure systems and peroxide hydrogen-abstraction cure systems, can deliver microreplication of acceptable quality but there are limitations shared by these systems: functional silicones, catalysts/initiators, thermal cycles, and byproducts. These limitations negatively affect silicone microreplication economically and from a processing standpoint.